Coronary angioplasty has emerged as a viable present alternative to bypass surgery for revascularization of stenotic and occluded coronary arteries. Percutaneous coronary angioplasty is less invasive and less traumatic to the patient and is less expensive since the angioplasty patient will have a shorter hospital stay and a shorter post-procedure recovery time.
Percutaneous transluminal angioplasty is performed by use of a catheter which has a built-in inflatable and deflatable balloon. The balloon catheter can be passed through a guiding catheter and advanced inside a target artery toward the point of obstruction that needs to be dilated. When the balloon portion of the catheter is properly positioned inside the arterial obstruction, the balloon is inflated to a pressure sufficient to overcome the resistance of the arteriosclerotic plaque of the obstructed site. By inflating the balloon in the stenosis multiple times over a period of time, the desired dilation of the obstructed segment of the artery can be achieved.
The distribution of atherosclerotic plaque in coronary arteries can have two major types of cross-sectional luminal shapes, concentric and eccentric. If the plaque is distributed evenly along the entire circumference of the arterial internal elastic membrane, the coronary lumen is located centrally and is called a concentric type lesion. If the plaque does not involve the entire arterial circumference leaving a variable arc of disease-free wall (normal wall), the residual cross-sectional lumen is called eccentric. More often than not, the lumen through a stenosis is off center and rarely round. Recent studies have found that a high percentage of arterial lesions are eccentric.
Ischemic complications of percutaneous translumina coronary angioplasty (PTCA) occur in a significant number of patients and constitute a major cause of morbidity and mortality associated with PTCA. Variable degrees of intimal and media and plaque disruption occur during all PTCA procedures and may vary from mild superficial splitting to gross fissuring through the entire medial and plaque mass.
As noted above, coronary occlusions are not always concentric relative to the diameter of the artery and, in fact, most such lesions have been found to be eccentric. The use of PTCA in a patient with an eccentric stenosis does not necessarily move the bulk of the stenotic material out of the arterial lumen. Very often, the thinner side of the lesion gives way and the artery wall gives way with it. Media layer tear or dissection is common. Although lumenal space is increased thereby increasing blood flow by the lesion, extensive damage may be done to the arterial wall. This damage is well documented in the following references:
"The Eccentric Coronary Atherosclerotic Plaque: Morphologic Observations and Clinical Relevance". B. F. Waller, M.D. Clinical Cardiology 12, 14-20 (1989) PA1 "Morphologic Correlate of Coronary Angiographics Patterns at the Site of PTCA". B. F. Waller, M.C. Clinical Cardiology 11,817-822 (1988) PA1 "Morphology of Coronary Lesions in the Prediction of Early PTCA Outcome". Haft et al, Catherization and Cardiovascular Diagnosis 17: 69-74 (1989) PA1 "Tear or Dissection After Coronary Angioplasty". King et al, Circulation--Volume 79, May 1989 pp. 1035-1041 PA1 "Vessel Plaque and Lumen Morphology After Transluminal Balloon Angioplasty". Lyon et at, Arteriosclerosis, Vol. 7, No. 3, May/June 1987 PA1 "Stress Analysis of the Diseased Arterial Cross Section". Vito, Whang, Giddens, Zadns, Glagov 1990. Advances in Bioengineering ASME, BED--Vol. 17
Very often balloon dilatation results in a situation where media and intima split along with the thin section of the stenosis. Because of material property (mechanical) differences within the stenotic material (it is not homogenous) and between the artery walls and the stenosis, delamination of the stenosis can also occur.
Detection of non-concentric lesions is easily done by using orthogonal views of the same anatomical area. Some lesions may look very minor in one view, but, when the same lesion is viewed at a fight angle to the first view, it may then seem extremely restrictive. Orthogonal viewing of the coronary arteries is very common and a long standing practice.
The consequence to lesion dissection is flow disruption which may lead to thrombus formation and early re-occlusion. It was hoped that the LABA [Laser Assisted Balloon Angioplasty] device would mitigate this problem. However, restenosis rates were not improved by this device.
The prior art includes patents disclosing a plurality of balloons positioned on the distal end of a dilation catheter as well as patents disclosing a plurality of lumens (luminae) having an inflatable lobe in communication with a respective tureen.
U.S. Pat. No. 4,787,388 to Hofmann discloses a multi-lobed balloon catheter having three lobes (balloons) that are independently and selectively inflatable by air passing through respective lumens communicating with the lobes. The Hofmann patent specifically teaches, however, that it is preferable for the balloons to be inflated together, such as from a common source (Col. 2, lines 46-54). The three balloons of the Hofmann catheter are formed independent from each other and form a triangular configuration (FIG. 3B). Because the balloons are separate from each other, the area between the balloons form passages which allow fluid flow between the balloons, thus forming a perfusion catheter. The balloons are substantially equal in size and preferably inflated together.
U.S. Pat. No. 5,071,406 to Jang discloses a balloon dilatation catheter having two or more independently inflatable balloons (FIG. 7) positioned on opposite sides of a catheter shaft. The first balloon has a longer length than the second balloon. The balloons share some common walls, and form a catheter construction having three effective diameters.
The catheter in Jang is constructed so that multiple balloons are formed from a single, monolithic piece of polymer material. This construction provides a smooth transition from balloon to balloon on the outside of the catheter. The balloons are formed so that one balloon may be longer and larger than the other balloon. One balloon is inflated while the other is deflated and, later, the inflated balloon is deflated and the deflated balloon inflated. The respective size of the inflated balloons thus varies for use in several stenoses or multi vessels.
U.S. Pat. No. 4,083,369 to Sinnreich discloses a surgical device used in gynecology. The device includes an inflatable balloon element formed of a relatively thicker wall area and an opposing thinner wall area. When the device is inserted within a body cavity, such as a uterus, the thinner wall area is adapted for contacting the raw tissues within a body cavity while the thicker wall section faces toward the less sensitive tissues, such as the forward abdominal wall.
U.S. Pat. No. 5,102,416 to Rock discloses a catheter having three expandable chambers that are selectively pressurized to cause the chambers to distend asymmetrically about the catheter's axis so that the catheter can be easily directed within a patient's venal system. Later, the chambers are equally inflated to provide a balloon which is symmetrical for use during an angioplasty procedure.
Other patents to Jang besides the '406 patent mentioned above include U.S. Pat. Nos. 4,744,366; 4,763,654; 4,958,634; and 4,990,139. These patents disclose concentrically arranged balloons, and balloons that are positioned proximal and distal to each other.
U.S. Pat. No. 5,108,370 to Walinsky discloses a perfusion balloon catheter in which the outer membrane forming the balloon is selectively connected to the inner tube of the catheter forming a perfusion tureen between a vascular wall and the outer membrane.
U.S. Pat. No. 5,000,734 to Boussignac et al discloses a probe having a bag element (balloon) with at least one perfusion conduit formed in the bag.
Other patents disclose multiple balloons, either positioned tandem to each other, or concentric to each other. Examples include U.S. Pat. Nos. 4,445,892; 4,778777; 4,748,981; 4,986,830; 4,994,033; 5,002,532; and 5,049,132.
Other patents disclose multiple lumen catheters such as U.S. Pat. Nos. 4,584,998 and 4,846,791.
There is a continuing need to provide safer and more efficient PCTA devices which can be used to help all patients including those having eccentric coronary occlusions.
It is an object of the present invention to provide unique PCTA devices which can focus the inflation energy of the balloon portion to a specific point on an arterial lesion.
It is further object of the present invention to provide the ability in a PCTA procedure to direct the dilating force(s) in desired direction(s).
It is a still further object of the present invention to provide a PCTA device which eliminates or minimizes the possible occurrence of arterial wall damage.